Thai police stand guard after a suspected insurgent attack at a military base in southern Thailand on Wednesday. Scores of heavily armed gunmen stormed the base in a major assault that left 16 militants dead.

By Amy Sawitta Lefevre, Reuters

BANGKOK -- A pre-dawn raid on a Thai military base ended with 16 militant Muslim insurgents killed on Wednesday in the deadliest violence in the country's south in nine years, marking a dangerous escalation in one of Asia's least-known conflicts.

Acting on a tip-off, marines lit flares and opened fire as up to 60 insurgents wearing military fatigues approached the base at about 1 a.m. local time in Narathiwat province on the Malaysian border, Internal Security Operations Command spokesman Pramote Phromin said. No Thai military members were hurt.

Violence is common in Thailand's south, but the scale of the attack and targeting of a marine base illustrate the difficulty Buddhist-majority Thailand faces in preventing the low-intensity Muslim insurgency from turning into a more dangerous conflict.

Surapan Boonthanom / Reuters

Thai security personnel investigate around bodies of insurgents at the site of an attack on a military base in the troubled southern province of Narathiwat on Wednesday.

Although there is no indication of the fighting spreading beyond the provinces of Pattani, Yala and Narathiwat, just a few hours' drive from some of Thailand's most popular tourist beaches, Prime Minister Yingluck Shinawatra appears powerless to quell the almost daily gunfights and bomb attacks.

"It was only going to be a matter of time before this type of incident happened," said Anthony Davis, a Thailand-based analyst at security consulting firm IHS-Jane's.

"The insurgents have been moving towards larger attacks on military bases since 2011. At the same time, there has been more proactive security intelligence work."

Experts say the insurgency is becoming better organized. Wednesday's death toll was the biggest since security forces stormed a mosque, known as the Krue Se mosque, in 2004, killing 32 Muslims in a raid that intensified the insurgency.

Since then, more than 5,300 people have been killed in the three provinces of Pattani, Yala and Narathiwat, where insurgents are seeking greater autonomy.

About 94 percent of the region's 1.7 million people are Muslim, the main religion in neighboring Malaysia and in nearby Indonesia, and about 80 percent of them speak a Malay dialect as a first language, according to a 2010 survey by the Asia Foundation.

In recent weeks, attacks have appeared bolder. Five soldiers were killed by suspected insurgents on Sunday. That followed a spate of attacks on civilians, including one this month in which four fruit traders from outside the region were found shot dead with their hands and legs bound.

The government is considering imposing a curfew in parts of the south, where the military already has wide-ranging powers of search and arrest under an emergency decree.